1. Technical Field
The present invention relates to the filtering of fluids and, more particularly, to an improved pleated filter as well as a method and apparatus for fabricating such filter.
The invention relates generally to the subject matter disclosed in U.S. Pat. Nos. 3,313,665, 3,377,220, 3,552,400 and 4,390,031. The subject matter disclosed in each of these patents is expressly incorporated herein, in its entirety, by reference.
2. Discussion of the Prior Art
It has long been recognized that pleated filters provide increased filter surface area as compared with filters having no pleats and the same exterior dimensions. However, there are a number of practical disadvantages inherent in prior art pleated filters which have severely limited the practical commercial use of such filters. For examle, the filter material which is to be pleated must be sufficiently structurally self-supporting so as to retain its shape when pleated. Thus, when thin membrane-like sheets of material are called for to perform the necessary filtering function, the structural integrity of the filter in pleated form requires the use of much thicker material. This occupies far more space than would be required for the thinner sheet of filter material, and also restricts the number of pleats permitted per linear inch of filter employed. Prior art attempts to provide a large number of pleats per inch have resulted in a closing off of the pleats, thereby restricting the available filter surface area. In addition, it has been impossible, heretofore, to provide a unitized depth filter in pleated form.